From mboxrd@z Thu Jan  1 00:00:00 1970
From: 'Christoph Hellwig' <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 16/16] dma-mapping: use exact allocation in
	dma_alloc_contiguous
Date: Fri, 14 Jun 2019 16:50:01 +0200
Message-ID: <20190614145001.GB9088@lst.de>
References: <20190614134726.3827-1-hch@lst.de>
	<20190614134726.3827-17-hch@lst.de>
	<a90cf7ec5f1c4166b53c40e06d4d832a@AcuMS.aculab.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
Content-Disposition: inline
In-Reply-To: <a90cf7ec5f1c4166b53c40e06d4d832a-1XygrNkDbNvwg4NCKwmqgw@public.gmane.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/iommu>,
	<mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/iommu/>
List-Post: <mailto:iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
List-Help: <mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/iommu>,
	<mailto:iommu-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=subscribe>
Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
To: David Laight <David.Laight-ZS65k/vG3HxXrIkS9f7CXA@public.gmane.org>
Cc: Maxime Ripard <maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org>, Joonas Lahtinen <joonas.lahtinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" <dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>, "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, 'Christoph Hellwig' <hch-jcswGhMUV9g@public.gmane.org>, "devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org" <devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org>, "linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, David Airlie <airlied-cv59FeDIM0c@public.gmane.org>, "linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Intel Linux Wireless <linuxwifi-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, "intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" <intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>, Maarten Lankhorst <maarten.lankhorst-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Jani Nikula <jani.nikula-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Ian Abbott <abbotti-GUHe90Wt2aFaa/9Udqfwiw@public.gmane.org>, Rodrigo Vivi <rodrigo.vivi-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Sean Paul <sean-p7yTbzM4H96eqtR555YLDQ@public.gmane.org>, "moderated list:ARM PORT" <linux-arm-kernel-IAPFreCvJWM1dQTEkxZZdg@public.gmane.org>
List-Id: dri-devel@lists.freedesktop.org

On Fri, Jun 14, 2019 at 02:15:44PM +0000, David Laight wrote:
> Does this still guarantee that requests for 16k will not cross a 16k boundary?
> It looks like you are losing the alignment parameter.

The DMA API never gave you alignment guarantees to start with,
and you can get not naturally aligned memory from many of our
current implementations.